Improved process of coating iron



1 UNITED STATES PATENT OFFICE.

E. G. POME'ROY, OF PHILADELPHIA, PENNSYLVANIA.

IMPROVED PROCESS OF COATING IRON.

Specification forming part of Letters Patent No. 18,409, dated October 13, 1857.

To all whom it may concern:

Be it known thatI, EBENEZER. G. POM'EROY, of the city of Philadelphia, in the State of Pennsylvania and United States of America, have discovered and reduced to practical use a new and useful method of effectually uniting copper or other metalssucl1 as gold, silver, nickel, zinc, tin, antimony, and bismuth, and their alloyswith the surface of iron.

To enable others skilled in the art of metallurgy to make and use this my invention, Iproceed to give the following description with respectto the manner of depositin galayer of copper or other metallic alloy upon the surface of theiron. As described by me in patents I have obtained in England and France, also in this country, this application may be looked upon as having no reference whatever.

The iron should be the best charcoal-bloom, sound and free from blisters or raw ore, and of uniform temper, for what I shall denolninate bronze iron. For spikes, bolts, bars, braces, bands, or other appliances for ship-building, the iron should be good sound common iron.

In preparing the iron for being rolled into sheets care will be required to obtain a surface free from indentation caused by scales of oxide being forced into the plates of iron in the process of rolling. The oxide-scale should be removed in time, so as to obtain a smooth surface similar to what is required for receiving a coat of tin. For more perfect work the iron should be rolled both ways to produce a crossfiber. The size 'of the plates to be bronzed should always correspond to the size required when finished, keeping in view the increase in length by rolling. For all other purposes the iron to receive the coat of bronze should be prepared in form and size required for use.

The surface of the iron must be cleansed from its oxide scales so as to. present a clean bright surface, and for that purpose I use a vat or bosh of a suitable size, lined with sheetlead, in which I dilute sulphuric acid or other acetous preparation of sufficient strength to remove the scales, then scour the surface until bright. It may then be deposited in a vat containing an alkaline preparation to prevent rusting. Lime should be avoided. It will deposit an insoluble sulphate that will prevent the bronze from taking. Soda-ash or potash is best. The articles may remain in this preparation until wanted for dipping in the bronze.

The form of a furnace most suitable for boldin g a bath of melted metal for covering sheets of iron is similar in form to a common puddling-furnace. Its length and breadth should be in proportion to the quantity of metal which you wish it to contain, having respect also to the size of the sheets to be bronzed. Its basin should be about twelve inches deep in the center, running from the center to a horizontal line at the surface at an angle of nearly forty degrees. The stack should be at the opposite end from the fire-house, and the door for introducing the metal to the bath should be in the center of the stack directly under the flue, so as to overcome the effects of a current of cold air that enters at the door. The current of hot air meeting the current of cold air, both pass up the fines and prevent the chilling effect that would otherwise be produced upon the metal. The crown of the furnace should correspond in shape to the form of a basin, so as to force the flame into the bottom of the basin to insure heat. The best materials for a furnace I have found to be first-class solid fire-brick, set in grout composed of fire-clay and plumbago. The form of the brick for the bottom should be that of a wedge with the thick end down, to prevent the bottom from rising up. 'Ihe sides shouldbe made of straight brick, laid in the same materials.

I will now consider the composition of the bath of metal copper alone, or alloyed to suit the fancy, as to substance, with any of the metals above described.

I have found from experience that in forming alloys at more solid and perfect alloy will be obtained by using the salts of sulphur or arsenic in a modified form, so as to produce a slight negative action Without injuring in any degree the tenacity of the alloy, and that al-' loys of pure metals will more readily combine with iron or with each other through the mineralizin g agency of the salts above mentioned. Now, fill your furnace with metal as you desire to a level with the bottom of the door-sill, to make it convenient for use and to prevent oxidation and evaporation. (lover the surface with a slag for its protection, formed of sand and clay mixed to a proper consistency, and when using push back the slag with a ravel some three or four inches, and fill the space 2 asaoo with borax. This will aid as a flux to the iron, keeping the metal in a fluid state, and insure a smooth surface to the bronze plate.

The manner of operating with the metal plates in the bath is as follows: Seize hold of the plate with suitable tongs, and plunge it into the bath of metal through the melted borax to a depth of more than half its length, and in a short time raiseit up and down in the metal bath and observe the progress of the amalgamation until it is perfect, when it will exhibit a very brilliant luminous appearance. Then withdraw the plate, handling it quickly in such a manner as to make the metal spread evenly on the surface, hold it up, and give the fluid metal a chance to retain an even thickness in the center of the sheet. Then lay it on .a turn-table, and quickly dip the other end of cleansing and preparing the same for use; the

form of the furnace and the manner of building the same; the kind of metal required for the bath, and its texture, and the manner of operating with the metal plates to effect the bronzing process. We now require another vat of sufficient size, lined with sheet-lead, to immerse the whole size of the metal plate in, containing diluted sulphuric acid, in which is contained nearly a saturated solution ofoXide of Copper or the sulphate-common blue vitriol of commerce. Hold the pieces to be bronzed in this solution until the surface exhibits a precipitated metallic surface of copper. This covering which now appears on the surface is a hydrated compound of the sulphate of iron and metallic copper, and when plunged into the bath of melted metal acts as a flux on the iron, and produces immediate molecular action and separation at a temperature much below a welding-heat. The result is a union of the fluid molecules of both metals, and the negative agency produces chemical union This plate, as taken from the first bath, is again immersed in a saturated solution of alum-water to protect the compound covering from oxidation while warming before dipping into the bronze-bath.

In rolling sheets great care should be taken in heating if a fire with a current of air and a flame is used, inasmuch as the bronze coating will be easily oxidized and greatly harmed thereby. Aclose muffle with a wood or charcoal fire is preferred for safety and to insure success.

This bronze-iron will be found usefulin many appliances where sheet copper, iron, or brass is now used in all parts of the construction of ships and other water-craft.

Having thus fully set forth and described the process of producing bronzed iron, I shall proceed to set forth and specify what I claim as my peculiar invention and discovery and desire to secure by Letters Patent, is:

The practical use and application of the hereinbefore-described solution of hydrated sulphate of iron and copper, brought in contact with the surface of the iron, in conjunction with the heat of the melted metal in the bath above described, thereby producing a molecular separation of the particles of the iron, giving to them the susceptibility of forming a perfect flowing union or fusion together with the aforesaid metals in the bath, in such a substantial manner as entirely to exclude a galvanic current between the iron and the surrounding alloys, or any or either of them.

EBENEZER Gr. POMEROY.

Witnesses:

WILLIAMS OGLE, HENRY T. GRoU'r. 

